In the field of automotive glass applications, one approach for making a defogger for a window is to apply a coating with conductive particles to a glass substrate and then fire the materials for securing the conductive particles in conductive electrical communication with each other. See, e.g., U.S. Pat. Nos. 7,138,347 and 5,795,501 (both incorporated by reference). This places potential restrictions upon the use of certain materials. For example, many transparent plastics will not withstand extreme conditions encountered during firing. In addition, with the costs and availability of energy resources for heating continuing to increase, it is desirable to reduce dependency upon energy intensive processes. In addition, many applications employ ceramic frit structures, such as in locations about their perimeters. Any such step of selectively applying a conductive layer to the substrate requires processing constraints for protecting the frit.
It is therefore desirable to have methods, compositions, and articles for realizing conductive substrates, particularly transparent substrates that can be manufactured easily without the need to subject the materials to extreme processing conditions.
One example of an effort to address improvements to window heaters is described in U.S. Pat. No. 7,129,444, incorporated by reference, which features grid lines made by dispersing a conductive metal in a polymeric matrix, particularly one that includes “an epoxy resin, a polyester resin, a polyvinyl acetate resin, a polyvinylchloride resin, a polyurethane resin or mixtures and copolymers of the like”. The examples address heat curing a heater grid onto a plastic window.
Ultraviolet (UV) curable compositions for use as heating elements are described in U.S. Pat. No. 6,946,628 (incorporated by reference). U.S. Pat. No. 6,174,606 (incorporated by reference) addresses a conductive composite including silver particles. U.S. Pat. No. 4,526,811, incorporated by reference, addresses a method to repair metal lines of window defoggers using a composition that “comprises (a) an acrylic ester polymer resin (b) a metallic pigment and (c) an organic pigment”. Other patents of potential interest include U.S. Pat. Nos. 6,290,881 and 6,713,000 (both incorporated by reference), which pertain to ultraviolet (UV) curable silver compositions. Examples of UV curable compositions include those in U.S. Pat. Nos. 7,119,129 and 6,784,223; both incorporated by reference. See also, U.S. Pat. Nos. 5,071,692; and 4,232,088, incorporated by reference.